• Turntable Geometry
• Illuminator of Opportunity
• Passive ISAR
• Range-Doppler technique
• Backprojection technique
• Ambiguity Function
• Borders Surveillance
• Fraunhofer FHR
• DVB-S
• Passive Radar
• Bistatic Radar
• DVB-S2

With ISAR (Invers Synthetic Aperture Radar) Imaging, we refer to a radar imaging technique able to generate two – dimensional high quality electromagnetic images of a target. The main difference with respect to the SAR (Synthetic Aperture Radar) techninque is that the target is not cooperative with the system, thus, its motion, instead of the transceiver motion, creates the synthetic aperture of the radar antenna.
The ISAR radars have a significant roles in surveillance scenarios, because they allow to obtain sufficiently high quality images for target recognition purposes. In situations where a normal radar display a single bright moving pixel on a screen, an ISAR image allows to discriminate between various target, such as missiles, military and civilian aircrafts and boats.
In the last years, the exploitation of others non – cooperative transmitters as Illuminators of Opportunity (IOOs) for radar application is become really important for many reasons, such as the unnecessary need of a dedicated transmitter, which significantly reduces the implementation costs. In case of military surveillance applications, the passive radar geometry of the system allows to get advantages in terms of RCS (Radar Cross Section), because a stealth target that is shaped to minimize its monostatic RCS may nevertheless have a higher bistatic RCS.
In this thesis work a DVB – S/S2 based passive ISAR radar is analyzed. The DVB – S and DVB – S2 (Second Generation) are the main standards for the television broadcastings using the geosynchronous satellites. These satellites are particularly interesting for the usage as illuminators of opportunity because, being geosynchronous over the Equator, they are always available and able to cover with their footprints a big area of the Earth surface.
After a short introduction about the general passive radar theory, the main characteristics of the DVB – S2 standard are explained, with a particular focus on the deterministic components contained into the signal that can cause some problems during the detection procedure.
In the third chapter, the ISAR imaging theory is explained, in particular the case of a bistatic configuration. Since we are interested in radar applications of these satellites, four different Ambiguity Functions will be presented, considering four different spectrum configurations of the signal. The evaluation of the performances in terms of range resolution and side lobe level (SLL) will be done.
Since this work is oriented on the evaluation of the possibility to obtained ISAR images using these satellites, a turning table has been used during the tests: this geometry allows the biggest aspect angle variation between the target and the radar.
In the fourth chapter the system, developed by the Fraunhofer FHR Institute, is introduced, evaluating the strong points and the main limitations. A case study to evaluate the efficiency of the system is presented.
In the fifth and final chapter, the experimental results are shown, in particular the ISAR images obtained using different image formation techniques. These images will be processed also with a Compressive Sensing technique to demonstrate the effectiveness of it in the grating lobes cancellation.